Fossil wood from the poorly dated (Jurassic–Cretaceous?) continental sediments of the Khorat Group, northeastern Thailand (Isan) is described. The Khorat Group is widely distributed (Laos, Cambodia and Thailand) and, despite its poorly known age, stratigraphy and palaeoecology, is of importance in understanding the Sibumasu–Indochina collision. The systematics of wood assemblage and palaeobiogeographical analysis reveal strong relationships with Indochina, especially Vietnam, and suggest an age in the range Middle Jurassic to Early Cretaceous. According to wood taphonomy, the corresponding trees grew alongside streams under a rather arid climate, although this became wetter during the deposition of the upper formations of the Khorat Group.